U.S. patent application number 17/046237 was filed with the patent office on 2021-02-04 for determining a location of a mobile device.
The applicant listed for this patent is ASSA ABLOY AB. Invention is credited to Hakan OLSSON.
Application Number | 20210033694 17/046237 |
Document ID | / |
Family ID | 1000005190357 |
Filed Date | 2021-02-04 |
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United States Patent
Application |
20210033694 |
Kind Code |
A1 |
OLSSON; Hakan |
February 4, 2021 |
DETERMINING A LOCATION OF A MOBILE DEVICE
Abstract
It is provided a method for determining a location of a mobile
device. The method comprises the steps of: obtaining a first
maximum distance between a first anchor point and the mobile
device; generating a first circular geometrical object having a
radius based on the first maximum distance; generating a first
polytope encompassing the first circular geometric object, wherein
all angles of the first polytope are right angles; obtaining a
second maximum distance between a second anchor point and the
mobile device; generating a second circular geometrical object
having radius based on the second maximum distance; generating a
second polytope encompassing the second circular geometric object,
wherein all angles of the second polytope are right angles; finding
a mobile device region as an overlap between the first polytope and
the second polytope; and determining that the mobile device is
located within the mobile device region.
Inventors: |
OLSSON; Hakan; (Hagersten,
SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASSA ABLOY AB |
Stockholm |
|
SE |
|
|
Family ID: |
1000005190357 |
Appl. No.: |
17/046237 |
Filed: |
April 15, 2019 |
PCT Filed: |
April 15, 2019 |
PCT NO: |
PCT/EP2019/059687 |
371 Date: |
October 8, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 5/12 20130101; G01S
5/0036 20130101 |
International
Class: |
G01S 5/00 20060101
G01S005/00; G01S 5/12 20060101 G01S005/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 19, 2018 |
EP |
18167916.8 |
Claims
1. A method for determining a location of a mobile device, the
method being performed in a location determiner and comprising:
obtaining a first maximum distance between a first anchor point and
the mobile device; generating a first circular geometrical object
centred on the first anchor point, having a radius based on the
first maximum distance; generating a first polytope encompassing
the first circular geometric object, wherein all angles of the
first polytope are right angles; obtaining a second maximum
distance between a second anchor point and the mobile device;
generating a second circular geometrical object, centred on the
second anchor point, having radius based on the second maximum
distance; generating a second polytope encompassing the second
circular geometric object, wherein all angles of the second
polytope are right angles; finding a mobile device region as an
overlap between the first polytope and the second polytope; and
determining that the mobile device is located within the mobile
device region.
2. The method according to claim 1, wherein at least one side of
the first polytope and at least one side of the second polytope are
parallel.
3. The method according to claim 2, wherein the sides of the first
polytope and the second polytope are aligned with axes of a
Cartesian coordinate system.
4. The method according to claim 1, further comprising: determining
that the mobile device is located within a target region then the
target region fully encompassed the mobile device region.
5. The method according to claim 1, wherein each side of the first
polytope ouches the encompassed first circular geometrical object
and each side of the second polytope touches the encompassed second
circular geometrical object.
6. The method according to claim 1, wherein the geometrical objects
are two dimensional objects, and the method further comprises:
finding intersection points between the first circular geometrical
object and the second circular geometrical object; and determining
which, if any, of the intersection points that can be applied to
restrict where the mobile device is located, and, when applicable,
finding the mobile device region comprises reducing the size of the
mobile device region based on the at least one applicable
intersection point.
7. The method according to claim 1, further comprising: obtaining a
third maximum distance between a third anchor point and the mobile
device, generating a third circular geometrical object, centred on
the third anchor point, having a radius based on the third maximum
distance; and generating a third polytope encompassing the third
circular geometric object, wherein all angles of the third polytope
are right angles; wherein finding an overlap comprises finding the
overlap between the first polytope, the second polytope and the
third polytope.
8. A location determiner for determining a location of a mobile
device, the location determiner comprising: a processor; and a
memory storing instructions that, when executed by the processor,
cause the location determiner to: obtain a first maximum distance
between a first anchor point and the mobile device generate a first
circular geometrical object, centred on the first anchor point,
having a radius based on the first maximum distance; generate a
first polytope encompassing the first circular geometric object,
wherein all angles of the first polytope are right angles; obtain a
second maximum distance between a second anchor point and the
mobile device; generate a second circular geometrical object,
centred on the second anchor point, having radius based on the
second maximum distance; generate a second polytope encompassing
the second circular geometric object, wherein all angles of the
second polytope are right angles; find a mobile device region as an
overlap between the first polytope and the second polytope; and
determine that the mobile device is located within the mobile
device region.
9. The location determiner according to claim 8, wherein at least
one side of the first polytope and at least one side of the second
polytope are parallel.
10. The location determiner according to claim 9, wherein the sides
of the first polytope and the second polytope are aligned with axes
of a Cartesian coordinate system.
11. The location determiner according to claim 8, further
comprising instructions that, when executed by the processor, cause
the location determiner to: determine that the mobile device is
located within a target region when the target region fully
encompassed the mobile device region.
12. The location determiner according to claim 8, wherein each side
of the first polytope touches the encompassed first circular
geometrical object and each side of the second polytope touches the
encompassed second circular geometrical object.
13. The location determiner according to claim 8, wherein the
geometrical objects are two dimensional objects, and the method
further comprises instructions that, when executed by the
processor, cause the location determiner to: find intersection
points between the first circular geometrical object and the second
circular geometrical object; and determine which, if any, of the
intersection points that can be applied to restrict where the
mobile device is located, and, when applicable, reduce the size of
the mobile device region based on the at least one applicable
intersection point.
14. A computer program for determining a location of a mobile
device, the computer program comprising computer program code
which, when run on a location determiner causes the location
determiner to: obtain a first maximum distance between a first
anchor point the mobile device; generate a first circular
geometrical object, centred on the first anchor point, having a
radius based on the first maximum distance; generate a first
polytope encompassing the first circular geometric object, wherein
all angles of the first polytope are right angles; obtain a second
maximum distance between a second anchor point and the mobile
device; generate a second circular geometrical object, centred on
the second anchor point, having radius based on the second maximum
distance; generate a second polytope encompassing the second
circular geometric object, wherein all angles of the second
polytope are right angles; find a mobile device region as an
overlap between the first polytope and the second polytope; and
determine that the mobile device is located within the mobile
device region.
15. A computer program product comprising a computer program
according to claim 14 and a computer readable means on which the
computer program is stored.
Description
TECHNICAL FIELD
[0001] The invention relates to a method, a location determiner, a
computer program and a computer program product for determining a
location of a mobile device.
BACKGROUND
[0002] Determining a location of a mobile device, such as a mobile
phone or key fob, can be achieved in many different ways. For
instance, the location of the mobile device can be determined by
measuring the distance from two or more known points and
determining the mobile device to be located at a point satisfying
the distance measurements. The accuracy is not perfect, whereby
there is a margin of error region around the estimated
location.
[0003] In most situations, it is acceptable that there is a certain
margin of error around an estimated location. However, when the
location of a mobile device needs to be evaluated with respect to a
target region, the presence of a margin of error is not optimal.
For instance, the margin of error region is both inside and outside
the target region, it is impossible to determine whether the mobile
device is inside or outside the target region. Moreover, even if
the mobile device most likely is located within the margin of error
region, this cannot be guaranteed. In other words, even if a margin
of error region is completely inside a target region, there is a
very small risk that the mobile device is actually outside the
margin of error region and can thus be outside the target
region.
[0004] US 2007/0268138 A1 discloses object a monitoring, locating
and tracking system, and a method employing RDID devices. US
2013/0329581 A1 discloses a method for positioning a mobile device
in a wireless wide area network. US 2014/0073351 A1 discloses
determining the location of mobile terminals in the presence of a
repeater. US 2013/0178235 A1 discloses a wireless communication
positioning method.
SUMMARY
[0005] It is an object to provide a way to determine a mobile
device region in which it can be guaranteed that a mobile device is
located.
[0006] According to a first aspect, it is provided a method for
determining a location of a mobile device. The method is performed
in a location determiner and comprises the steps of: obtaining a
first maximum distance between a first point first anchor point and
the mobile device; generating a first circular geometrical object,
centred on the first anchor point, having a radius based on the
first maximum distance; generating a first polytope encompassing
the first circular geometric object, wherein all angles of the
first polytope are right angles; obtaining a second maximum
distance between a second anchor point and the mobile device;
generating a second circular geometrical object, centred on the
second anchor point, having radius based on the second maximum
distance; generating a second polytope encompassing the second
circular geometric object, wherein all angles of the second
polytope are right angles; finding a mobile device region as an
overlap between the first polytope and the second polytope, and
determining that the mobile device is located within the mobile
device region.
[0007] At least one side of the first polytope and at least one
side of the second polytope may be parallel.
[0008] The sides of the first polytope and the second polytope may
be aligned with axes of a Cartesian coordinate system.
[0009] The method may further comprise the step of: determining
that the mobile device is located within a target region when the
target region fully encompassed the mobile device region.
[0010] Each side of the first polytope may touch the encompassed
first circular geometrical object and each side of the second
polytope touches the encompassed second circular geometrical
object.
[0011] The geometrical objects may be two dimensional objects, and
the method further comprises the step of: finding intersection
points between the first circular geometrical object and the second
circular geometrical object; and determining which, if any, of the
intersection points that can be applied to restrict where the
mobile device is located, and, when applicable, the step of finding
the mobile device region comprises reducing the size of the mobile
device region based on the at least one applicable intersection
point.
[0012] The method may further comprise the steps of: obtaining a
third maximum distance between a third anchor point and the mobile
device; generating a third circular geometrical object, centred on
the third anchor point, having a radius based on the third maximum
distance; and generating a third polytope encompassing the third
circular geometric object, wherein all angles of the third polytope
are right angles; wherein the step of finding an overlap comprises
finding the overlap between the first polytope, the second polytope
and the third polytope.
[0013] According to a second aspect, it is provided a location
determiner for determining a location of a mobile device. The
location determiner comprises: a processor; and a memory storing
instructions that, when executed by the processor, cause the
location determiner to: obtain a first maximum distance between a
first anchor point and the mobile device;
[0014] generate a first circular geometrical object, centred on the
first anchor point, having a radius based on the first maximum
distance; generate a first polytope encompassing the first circular
geometric object, wherein all angles of the first polytope are
right angles; obtain a second maximum distance between a second
anchor point and the mobile device; generate a second circular
geometrical object, centred on the second anchor point, having
radius based on the second maximum distance; generate a second
polytope encompassing the second circular geometric object, wherein
all angles of the second polytope are right angles; find a mobile
device region as an overlap between the first polytope and the
second polytope; and determine that the mobile device is located
within the mobile device region.
[0015] At least one side of the first polytope and at least one
side of the second polytope may be parallel.
[0016] The sides of the first polytope and the second polytope may
be aligned with axes of a Cartesian coordinate system.
[0017] The location determiner may further comprise instructions
that, when executed by the processor, cause the location determiner
to: determine that the mobile device is located within a target
region when the target region fully encompassed the mobile device
region.
[0018] Each side of the first polytope may touch the encompassed
first circular geometrical object and each side of the second
polytope may touch the encompassed second circular geometrical
object.
[0019] The geometrical objects may be two dimensional objects, and
the method may further comprise instructions that, when executed by
the processor, cause the location determiner to: find intersection
points between the first circular geometrical object and the second
circular geometrical object; and determine which, if any, of the
intersection points that can be applied to restrict where the
mobile device is located, and, when applicable, reduce the size of
the mobile device region based on the at least one applicable
intersection point.
[0020] According to a third aspect, it is provided a computer
program for determining a location of a mobile device. The computer
program comprises computer program code which, when run on a
location determiner causes the location determiner to: obtain a
first maximum distance between a first anchor point and the mobile
device; generate a first circular geometrical object, centred on
the first anchor point, having a radius based on the first maximum
distance; generate a first polytope encompassing the first circular
geometric object, wherein all angles of the first polytope are
right angles; obtain a second maximum distance between a second
anchor point and the mobile device; generate a second circular
geometrical object, centred on the second anchor point, having
radius based on the second maximum distance; generate a second
polytope encompassing the second circular geometric object, wherein
all angles of the second polytope are right angles; find a mobile
device region as an overlap between the first polytope and the
second polytope; and determine that the mobile device is located
within the mobile device region.
[0021] According to a fourth aspect, it is provided a computer
program product comprising a computer program according to the
third aspect and a computer readable means on which the computer
program is stored.
[0022] Generally, all terms used in the claims are to be
interpreted according to their ordinary meaning in the technical
field, unless explicitly defined otherwise herein. All references
to "a/an/the element, apparatus, component, means, step, etc." are
to be interpreted openly as referring to at least one instance of
the element, apparatus, component, means, step, etc., unless
explicitly stated otherwise. The steps of any method disclosed
herein do not have to be performed in the exact order disclosed,
unless explicitly stated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The invention is now described, by way of example, with
reference to the accompanying drawings, in which:
[0024] FIG. 1 is a schematic diagram illustrating how small
inaccuracies of location determination can have crucial effects for
security applications;
[0025] FIG. 2 is a schematic diagram illustrating determination of
a mobile device region with great certainty in two dimensions
according to one embodiment;
[0026] FIG. 3 is a schematic diagram illustrating the determination
of a mobile device region with greater accuracy by exploiting
intersection points;
[0027] FIG. 4 is a schematic diagram illustrating determination of
a mobile device region with great certainty in three dimensions
according to one embodiment;
[0028] FIG. 5 is a flow chart illustrating a method for determining
a location of a mobile device;
[0029] FIG. 6 is a schematic diagram illustrating how intersection
points location in relation to anchor points can limit the mobile
device region, when the first anchor point is above the second
anchor point;
[0030] FIG. 7 is a schematic diagram illustrating how intersection
points location in relation to anchor points can limit the mobile
device region, when the first anchor point is below the second
anchor point;
[0031] FIG. 8 is a schematic diagram illustrating components of the
location determiner of FIG. 1; and
[0032] FIG. 9 shows one example of a computer program product 90
comprising computer readable means.
DETAILED DESCRIPTION
[0033] The invention will now be described more fully hereinafter
with reference to the accompanying drawings, in which certain
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided by way of example so that this
disclosure will be thorough and complete, and will fully convey the
scope of the invention to those skilled in the art. Like numbers
refer to like elements throughout the description.
[0034] Embodiments presented herein exploit the fact that a mobile
device cannot be located outside a maximum distance from a
measurement point. The measurements define circles (in two
dimensions) or spheres (in three dimensions), which, where they
overlap contain the mobile device. Additionally, in order to save
resource usage, the circles are replaced by polytopes (typically
square/cube), for which the overlap can be calculated more
efficiently. Significantly, the mobile device can be guaranteed to
be located within the overlapping area, which can be exploited e.g.
to conclusively determine when a mobile device is within a target
area or not.
[0035] FIG. 1 is a schematic diagram illustrating how small
inaccuracies of location determination can have crucial effects for
security applications.
[0036] A target region 9 can e.g. be a building or part of a
building, such as a flat or an office. There are here a first
anchor point boa and a second anchor point 10b. At the first anchor
point, there is a distance measurement device which can measure the
distance to a mobile device 2. The distance can e.g. be measured
using Time of Flight (ToF). With ToF, the distance to the mobile
device is measured by the time it takes for a radio signal to
travel to the mobile device 2 and/or back to the distance
measurement device.
[0037] A location determiner 1 is used to determine the location of
the mobile device 2. The location determiner 1 can be a stand-alone
device, or it can be housed in another device, such as a device at
the first anchor point boa or the second anchor point 10b for
measuring distance. When the location determiner is implemented in
a battery powered device, it is of utmost importance to conserve
resource usage for the location determination.
[0038] When the distance measurements are used to determine whether
the mobile device 2 is inside or outside the target region 9, small
differences can have serious effects.
[0039] In the prior art, the location of the mobile device can be
determined by measuring the distance from the two points 10a, 10b
and determining the mobile device to be located at a point
satisfying both distance measurements. The accuracy is not perfect,
whereby there is a margin of error region 3 around the estimated
location. When the margin of error region 3 is both inside and
outside the target region, it is impossible for the location
determiner 1 to determine whether the mobile device 2 is inside or
outside the target region 9. Moreover, even if the mobile device 2
most likely is located within the margin of error region 3, this
cannot be guaranteed.
[0040] However, using embodiments presented herein, the location
determiner can determine the location of a mobile device region in
which it can be guaranteed that the mobile device is located, and
this is performed in a resource efficient manner.
[0041] FIG. 2 is a schematic diagram illustrating determination of
a mobile device region with great certainty in two dimensions
according to one embodiment. There is here a first anchor point boa
from which it can be measured a distance to a mobile device. For
instance, ToF can be used, the propagation time of a radio signal
is used to determine a first maximum distance 11a between the first
anchor point boa and the mobile device 2. When e.g. ToF is used,
the first maximum distance 11a can be determined on the speed of
light. While a delay can be introduced by processing, etc., this
would only be reflected in that the mobile device is closer than
indicated by the first maximum distance 11a. The only way that the
mobile device could be located outside the first maximum distance
11a if signal speeds greater than the speed of light is achieved,
which is not possible. A first circular geometrical object 12a is
generated based on the first maximum distance 11a, such that the
first circular geometrical object 12a is centred on the first
anchor point boa and has a radius which is the first maximum
distance 11a. Since the scenario of FIG. 2 is in two dimensions,
the first circular geometric object 12a is here a circle.
[0042] Based on the first maximum distance 11a, it can be safely
guaranteed that the mobile device 2 is within the first circular
geometrical object 12a.
[0043] Analogously, is can be guaranteed that the mobile device 2
is within a second circular geometrical object 12b, which is
generated in accordance with how the first circular geometric
object 12a is generated.
[0044] By combining the first circular geometrical object 12a and
the second circular geometrical object 12b, it could be determined
that the mobile device 2 is located within a section where the
circular geometrical objects 12a, 12b overlap. However, determining
this section is computationally expensive, especially if more
maximum distances and corresponding circular geometrical objects
are applied.
[0045] According to embodiments herein, the location of the mobile
device is determined in a more computationally efficient manner by
additional simplifications. A first polytope 13a is generated which
encompasses the first circular geometric object 12a. All angles of
the first polytope 13a are right angles. Since the scenario of FIG.
2 is in two dimensions, the first polytope 13a is a, or more
specifically a square. More specifically, when the size of the
first polytope 13a is minimal in size, but still encompassing the
first circular geometric object 12a, the first polytope 13a is a
square. The same procedure is repeated for the second circular
geometric object 12b, resulting in a second polytope 13b being here
a rectangle or a square.
[0046] Since the first and second circular geometrical objects
12a-b are respectively encompassed by the first and second
polytopes 13a-b, an overlap 16 between the first and second
polytopes 13a-b necessarily contains the overlap between the first
and second circular geometrical objects 12a-b. In other words, the
mobile device 2 must be located within the overlap 16 between the
first and second polytopes 13a-b.
[0047] The calculation of the rectangular (in two dimensions)
overlap 16 between the two polytopes 13a-b is very computationally
efficient.
[0048] The implication of this is significant, since when the
overlap 16 between the first and second polytopes 13a-b is located
e.g. within a target space (9 of FIG. 1), it can be deduced that
the mobile device 2 must also be located within the target space,
which relies on the speed of light for radio signals not being
exceeded.
[0049] More points and maximum distances can be applied to reduce
the size of the overlap 16, and thus the accuracy of the location
determination.
[0050] In other words, the maximum distances 11a, 11b are used in a
computationally effective way to determine a mobile device region
15 in which the mobile device must be located.
[0051] FIG. 3 is a schematic diagram illustrating the determination
of a mobile device region with greater accuracy by exploiting
intersection points.
[0052] The scenario of FIG. 3 is similar to that of FIG. 2, but
here, a first intersection point 17a and a second intersection
point 17b are indicated. The intersection points 17a, 17b are where
the first circular geometrical shape 12a and the second circular
geometrical shape 12b intersect.
[0053] The intersection points 17a, 17b are used to reduce the size
of the mobile device region 15, where, as for FIG. 2, must contain
the mobile device 2.
[0054] Looking at the second intersection point 17b, the entire
overlap between the circular geometrical objects is below the
second intersection point 17b. Hence, the mobile device 2 must be
located below the second intersection point 17b. This knowledge is
used to reduce the mobile device region 15 by reducing the height
of the mobile device region 15 to the second intersection point
17b.
[0055] By reducing the size of the mobile device region 15, the
accuracy is improved, since there is a smaller mobile device region
15 in which the mobile device 2 is known to be located.
Nevertheless, the certainty that the mobile device is in the mobile
device region 15 is not compromised with this procedure.
[0056] FIG. 4 is a schematic diagram illustrating determination of
a mobile device region with great certainty in three dimensions
according to one embodiment. In other words, the embodiments
presented and described above can be expanded to three
dimensions.
[0057] When applied in three dimensions, the first polytope 13a and
the second polytope are cubes or cuboids. The overlapping region 16
between the first polytope 13a and the second polytope 13b is in
the shape of a cuboid or a cube. Hence, the mobile device region 15
is also in the shape of a cuboid or a cube.
[0058] While not shown in FIG. 4, the first circular geometrical
object 12a and the second circular geometrical object 12b are here
both in the shape of a sphere.
[0059] FIG. 5 is a flow chart illustrating a method for determining
a location of a mobile device. The method is performed in a
location determiner.
[0060] In an obtain 1.sup.st max distance step 40, the location
determiner obtains a first maximum distance between a first anchor
point and the mobile device.
[0061] In a generate 1.sup.st circular object step 42, the location
determiner generates a first circular geometrical object. The first
circular geometrical object is centred on the first anchor point
and has a radius which is based on the first maximum distance. When
applied in two dimensions, the first circular geometrical object is
a circle and when applied in three dimensions, the first circular
geometrical object is a sphere.
[0062] In a generate 1.sup.st polytope step 44, the location
determiner generates a first polytope encompassing the first
circular geometric object. All angles of the first polytope are
right angles. When applied in two dimensions, the polytope is a
rectangle or square, and when applied in three dimensions, the
polytope is a cuboid or cube.
[0063] In one embodiment, each side of the first polytope touches
the encompassed first circular geometrical object.
[0064] In an obtain 2.sup.nd max distance step 46, the location
determiner obtains a second maximum distance between a second
anchor point and the mobile device. It is to be noted that this
step is performed close in time to step 40 to prevent
miscalculations due to the mobile device moving between obtaining
the different distances. For instance, step 40 and 46 can be
performed within a threshold time of each other.
[0065] In a generate 2.sup.nd circular object step 48, the location
determiner generates a second circular geometrical object. The
second circular geometrical object is centred on the second anchor
point and has a radius which is based on the second maximum
distance. When applied in two dimensions, the second circular
geometrical object is a circle and when applied in three
dimensions, the second circular geometrical object is a sphere.
[0066] In a generate 2.sup.nd polytope step 50, the location
determiner generating a second polytope encompassing the second
circular geometric object. All angles of the second polytope are
right angles. When applied in two dimensions, the polytope is a
rectangle or square, and when applied in three dimensions, the
polytope is a cuboid or cube.
[0067] In one embodiment, each side of the second polytope touches
the encompassed second circular geometrical object.
[0068] In one embodiment, at least one side of the first polytope
and at least one side of the second polytope are parallel. For
instance, the sides of the first polytope and the second polytope
can be aligned with axes of a Cartesian coordinate system. This
significantly simplifies calculation of overlap.
[0069] In an optional obtain 3.sup.rd max distance step 56, the
location determiner obtains a third maximum distance between a
third anchor point and the mobile device.
[0070] In an optional generate 3.sup.rd circular object step 58,
the location determiner generates a third circular geometrical
object. The third circular geometrical object is centred on the
third anchor point and has a radius based on the third maximum
distance. When applied in two dimensions, the third circular
geometrical object is a circle and when applied in three
dimensions, the third circular geometrical object is a sphere.
[0071] In an optional generate 3.sup.rd polytope step 59, the
location determiner generates a third polytope encompassing the
third circular geometric object. All angles of the third polytope
are right angles. When applied in two dimensions, the polytope is a
rectangle or square, and when applied in three dimensions, the
polytope is a cuboid or cube.
[0072] It is to be noted that steps 56, 58 and 59 can optionally be
repeated respectively for an arbitrary number of anchor points, and
thus maximum distances, circular objects and polytopes, i.e. for a
fourth anchor point, a fifth anchor point, etc. More anchor points
result in a smaller mobile device region, and thus greater
accuracy.
[0073] In an optional find intersections step 51, the location
determiner finds, for the two-dimensional case, intersection points
(see 17a-b of FIG. 3) between the first circular geometrical object
and the second circular geometrical object.
[0074] Intersections can have the ability to, but do not need to,
contribute to reducing the size of the mobile device region.
[0075] Intersection points 17 are now explained a bit further with
reference to FIG. 6, where intersection points 17 are illustrated
in relation to the first anchor point boa and the second anchor
point bob. Different potential sections 19a-j are shown where
intersection points 17 can occur, based mainly on a combination of
quadrants of the two anchor points. When applied as explained
below, the mobile device region can be reduced by one or two
straight lines, reflecting that the mobile device is to the right
or left, and/or above or below the intersection point 17.
[0076] The relations illustrated in FIG. 6 can be used to determine
whether an intersection point 17 can contribute to reducing the
size of the mobile device region.
[0077] When the intersection point 17 is located in the same
quadrants of both the first anchor point and the second anchor
point, see the first section 19c, the third section 19c, the eighth
section 19h, and the tenth section 19j, the intersection point 17
does not contribute.
[0078] In other words, when the intersection point 17 is located in
the third section 19c, which is defined by the first quadrant of
the first anchor point boa and the first quadrant of the second
anchor point 10b, the intersection point 17 does not contribute.
When the intersection point 17 is located in the first section 19a,
which is defined by the second quadrant of the first anchor point
boa and the second quadrant of the second anchor point 10b, the
intersection point 17 does not contribute. When the intersection
point 17 is located in the eighth section 19h, which is defined by
the third quadrant of the first anchor point boa and the third
quadrant of the second anchor point 10b, the intersection point 17
does not contribute. When the intersection point 17 is located in
the tenth section 19j, which is defined by the fourth quadrant of
the first anchor point boa and the fourth quadrant of the second
anchor point 10b, the intersection point 17 does not
contribute.
[0079] When the intersection point 17 is located in the second
section 19b, which is defined by the first quadrant of the first
anchor point boa and the second quadrant of the second anchor point
10b, the mobile device is below the intersection point 17.
[0080] When the intersection point 17 is located in the fourth
section 19d, which is defined by the third quadrant of the first
anchor point boa and the second quadrant of the second anchor point
10b, the mobile device is to the right of the intersection point
17.
[0081] When the intersection point 17 is located in the ninth
section 19i, which is defined by the fourth quadrant of the first
anchor point boa and the third quadrant of the second anchor point
10b, the mobile device is above the intersection point 17.
[0082] When the intersection point 17 is located in the seventh
section 19g, which is defined by the fourth quadrant of the first
anchor point boa and the first quadrant of the second anchor point
10b, the mobile device is to the left of the intersection point
17.
[0083] When the intersection point 17 is located in the fourth
quadrant of the first anchor point boa and the second quadrant of
the second anchor point 10b, the intersection point can be either
in the fifth section 19e or the sixth section 19f. The distinction
between the fifth section 19e and the sixth section 19f is based on
whether the intersection point 17 is above (for the fifth section
19e) or below (for the sixth section 19f) a straight line 20
between the first anchor point boa and the second anchor point
10b.
[0084] When the intersection point 17 is located in the fifth
section 19e, the mobile device is both below and to the left of the
intersection point 17. When the intersection point 17 is located in
the sixth section 19f, of the intersection point.
[0085] For the three-dimensional case, the location determiner
finds intersecting lines between the first circular geometrical
object and the second circular geometrical object.
[0086] In an optional determine restriction(s) based on
intersections step 52, the location determiner determines which, if
any, of the intersection points that can be applied to restrict
where the mobile device is located.
[0087] In a find mobile device region step 53, the location
determiner finds a mobile device region as an overlap between the
first polytope and the second polytope.
[0088] When there are three polytopes, this step comprises finding
the overlap between the first polytope, the second polytope and the
third polytope.
[0089] When applicable, the step of finding the mobile device
region comprises reducing the size of the mobile device region
based on the at least one applicable intersection point.
[0090] In determine mobile device location step 54, the location
determiner determines that the mobile device is located within the
mobile device region. In other words, the location is not here a
specific point, but a region.
[0091] In an optional determine whether m.d. (mobile device) in
target region step 55, the location determiner determines that the
mobile device is located within a target region when the target
region fully encompassed the mobile device region.
[0092] FIG. 8 is a schematic diagram illustrating components of the
location determiner 1 of FIG. 1. It is to be noted that one or more
of the mentioned components can be shared with a host device. The
location determiner 1 can be battery powered, whereby resources are
very limited in order to preserve battery life. A processor 60 is
provided using any combination of one or more of a suitable central
processing unit (CPU), multiprocessor, microcontroller, digital
signal processor (DSP), etc., capable of executing software
instructions 67 stored in a memory 64, which can thus be a computer
program product.
[0093] The processor 60 could alternatively be implemented using an
application specific integrated circuit (ASIC), field programmable
gate array (FPGA), etc. The processor 60 can be configured to
execute the method described with reference to FIG. 5 above.
[0094] The memory 64 can be any combination of random-access memory
(RAM) and/or read-only memory (ROM). The memory 64 also comprises
persistent storage, which, for example, can be any single one or
combination of magnetic memory, optical memory, solid-state memory
or even remotely mounted memory.
[0095] A data memory 66 is also provided for reading and/or storing
data during execution of software instructions in the processor 60.
The data memory 66 can be any combination of RAM and/or ROM.
[0096] The location determiner 1 further comprises an I/O interface
62 for communicating with other external entities. Optionally, the
I/O interface 62 also includes a user interface.
[0097] Other components of the location determiner 1 are omitted in
order not to obscure the concepts presented herein.
[0098] FIG. 9 shows one example of a computer program product 90
comprising computer readable means. On this computer readable
means, a computer program 91 can be stored, which computer program
can cause a processor to execute a method according to embodiments
described herein. In this example, the computer program product is
an optical disc, such as a CD (compact disc) or a DVD (digital
versatile disc) or a Blu-Ray disc. As explained above, the computer
program product could also be embodied in a memory of a device,
such as the computer program product 64 of FIG. 8. While the
computer program 91 is here schematically shown as a track on the
depicted optical disk, the computer program can be stored in any
way which is suitable for the computer program product, such as a
removable solid-state memory, e.g. a Universal Serial Bus (USB)
drive.
[0099] The invention has mainly been described above with reference
to a few embodiments. However, as is readily appreciated by a
person skilled in the art, other embodiments than the ones
disclosed above are equally possible within the scope of the
invention, as defined by the appended patent claims.
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